In a front-engine front-drive type vehicle, in which an engine and a transmission are connected in an axial direction and are transversely mounted, various attempts have been made to reduce the size of the transmission and to enhance torque. For example, as disclosed in JP 2002-70960A (hereinafter, referred to as reference 1), one input shaft and two counter shafts are provided and plural gear sets are arranged in parallel to each other between the input shaft and each of the counter shafts, thereby reducing axial length of the transmission while including plural speed shift stages. FIG. 5 illustrates a transmission 1 which includes substantially the same structure as a second embodiment of the reference 1, in which six gear sets are provided. In a transmission case 2, an input shaft 3a and first and second counter shafts 3b, 3c are arranged in parallel to each other. Further, first to fourth gear sets are provided between the input shaft 3a and the first counter shaft 3b. A first switching clutch 5A is provided between the first gear set and the second gear set. A second switching clutch 5B is provided between the third gear set and the fourth gear set. Still further, fifth and sixth gear sets are provided between the input shaft 3a and the second counter shaft 3c. A third switching clutch 5C is provided between the fifth and sixth gear sets. The input shaft 3a is driven to rotate by the engine 10. The first and second counter shafts 3b and 3c are connected to output shafts 8a and 8b via final reduction gears 6a, 6b, 6c and a differential mechanism 7. Further, a reverse movement gear mechanism 4C, which includes a reverse gear set and a reverse switching clutch 5D, is provided between the second counter shaft 3c and a reverse shaft 3d arranged in parallel with the input shaft 3a. 
According to the reference 1, in the transmission 1 including the six forward speed shift gear sets, a first gear mechanism 4A (including the first to fourth gear sets and the first and second switching clutches 5A, 5B) mounted between the input shaft 3a and the first counter shaft 3b and a second gear mechanism 4B (including the fifth and sixth gear sets and the third switching clutch 5C) mounted between the input shaft 3a and the second counter shaft 3c are arranged to be in parallel with each other. Accordingly, an entire axial length of the transmission 1 can be reduced in comparison with a transmission, in which gear mechanisms are provided between an input shaft and one counter shaft, in a case where the member of the speed shift stages is the same between such type of transmission and the transmission 1 disclosed in the reference 1. However, because the four forward movement gear sets (the first to fourth gear sets) and the two shifting clutches 5A, 5B are mounted to the first counter shaft 3b, the length of the first counter shaft 3b requires to be longer than that of the second counter shaft 3c, at which the two forward speed shift gear sets (the fifth and sixth gear sets) and the two shifting clutches 5C and 5D are provided, by the length of one gear set. Therefore, in a case where the length of the first counter shaft 3b and that of the second counter shaft 3c are arranged to be the same, a useless space is generated at the second counter shaft 3c. 
A need thus exists for a transmission with a multi-gear set, which is not susceptible to the drawback mentioned above.